Electromagnetic actuator



Oct. 19, 1954 L. E. LAWRENCE ELECTROMAGNETIC ACTUATORS m f IN #Ww w zswy/ 4 f o ,EL L f 2 y gli, f, /a

5gg; c I/ 2f 7 f 7 l, f5 L, ZJ? m lf f wf a W mm m* w 0/ g /w f Oct. 19, 1954 L. E. LAWRENCE ELECTROMAGNETIC AcTUAToRs Filed June 16, 1952 4 Sheets-Sheet 3 Oct. 19, 1954 L. E. LAWRENCE ELECTROMAGNETIC ACTUATORS 4 Sheets-Sheet 4 Filed June 16, 1952 i INVENTOR. YM W B yzz'of/y@ mw o l Patentecl Olot. 19, 1954 UNITED srArss tamis This invention relatesto an electro-magnetic yactuator suitable for causing motion for such purposes as the opening andclosing of switch contacts, the operation of valves and other mechanical instrumentalities, and it more specifically resides in an actuator having a coil, a yoke extendalong the exterior of the coil and an armature extending through the coil in mutually attractahle relation to the yoke, the armature being smaller in cross sectionthan the inside opening of the coil and being guided for translatory movement in parallel attitudes across the axis of the coil in response to energization of the coil.

For many purposes, vpartici'ilarly for the actuation of switches having .preloaded spring hacked contacts, it is desirable that the magnet employed not stop in its closing movement ai'ter. initial en gagement of the contacts and priorto sealing of the magnet. Toavoid partial closurevit isimportant that an electro-magneticallyactuated switch have pull-in characteristics such that motion'to sealed position is inevitable at any voltage equal to or in excess of pickup voltage. To this fend it is desirable to provide a magnet in which pickup'voltage is or can be made comparable to,

lor greater than the voltage required for the magnetto overcome the maximum opening forces encountered during compression of the contact springs. l

A actuating electro-magnets also are in essence single stroke electricmotors which usually are called upon to function over a long life without lubrication. It is desirable therefore that rubbing surfaceasubject to wear, employed to guide the `motion of the parts be as lightly loa-ded as possible. To this end it is important to not impose upon the wearing surfaces of the guides employed for es arisingfrom directly acting magnetic attraction.

it is desirahie also that an electro-magnet be compact in relation to'its power; that it be simple, economical and rugged in its construction; and that he versatile in that it may be modied without undue expense to meet the requirements of various loads to be actuated.

With these and other considerations in View an electro-'nagnetic actuator is provided in accordance with this invention in which an armature is mounted in a` coil wound large enough to permit motion of the armature across the axis of the coil and an external yoke running along the outside `of the coil is disposed to gather flux to cause an attractive force to he exerted on the armature in the direction of movement of the armature. which `for convenience herein is referred to as transverse movement, the whole being combined in novel fashion with guiding means which engage the ends of the armature and join with Vparts which transmit the actuating force.

It is an object of this invention to provide an electro-magnetic actuator in which the attractive force between yoke and armature due to the magnetic eld, in open position, is opposed by a magnetically induced force which diminishes to a negligible quantity as the magnetic actuator `moves to closed position.

lt is another object ci this invention to provide an electro-magnetic actuator in whichthe armature is disposed within a coiland is translated. transversely and in a straight line to a sealed position with a yoke which it meets at two sets, ci sealing surfaces through which the total working iiux passes when the magnet is closed.

it is still another object of this invention to `support an armature in the central opening of a coil for movement in a straightline in parallel `attitudes'transversely of the coil opening.

A further object of this invention is to diminish the side -play and endl play of the armature of an electro-magnet hy the provision of bearing surfaces that maintain the alignment of the armature with respect to the yoke' within narrow limits.

Another object of this invention is to provide a magnet in which side pull on the armature is relatively small so as to reduce wear of the armature guiding means.

It is a further object of this invention to provide a supporting and guiding structure for an A armature for guiding the movement of the armature and for transmitting such motion to the movable contacts of an electro-magnetic switch.

It is another object of this invention to provide ayoke and armature capable `of limited accomp modating movement v/ith respect to one another about two perpendicular axes, to permit self alignment oi the sealing 'surfaces between them.

It is a further object of this invention to provide an arc hood for an electro-magnetic switch of the class described, which arc hood includes stationary contact assemblies that may be reymoved to expose vthe same for inspection.

These and other objects and advantages will yappear in the description to follow. In the debroken away and in section of an electro-mag- 3 netic switch in which this invention may be embodied,

Fig. 2 is a side view in cross section of the electro-magnetic switch shown in Fig. l viewed through the plane 2 2,-

Fig. 3 is a front view in elevation with parts broken away and in section of the electro-magnetic switch shown in Figs. l and 2 with the armature thereof in sealed or closed position,

Fig. 4 is a fragmentary front view in elevation with parts broken away and in section of a modication of the electro-magnetic switch shown in Figs. l, 2 and 3 having a supplementary yoke positioned beneath the armature,

Fig. 5 is a perspective view of the magnetic yoke of the electro-magnetic switch shown in Figs. l, 2 and 3,

Fig. 6 is a perspective view oi the eld support member of the electromagnetic switch shown in Figs. l, 2 and 3,

Fig. 7 is a perspective view of the magnetic armature of the electro-magnetic switch shown in Figs. l, 2 and 3,

Fig. S is a perspective View of the armature carrier or" the electro-magnetic switch shown in Figs. l, 2 and 3,

Fig. 9 is a perspective View of the magnetic yoke and the magnetic armature of the switch shown in Figs. l, 2 and 3 in open position and with the actuating coil schematically represented in its position relative to the yoke and armature, and

Fig. 10 is a perspective View ci the magnetic components of the modification of Fig. -i with' the actuating coil schematically represented.

Referring now to the drawings and more particularly to Figs. 1, 2 and 3, there is shown therein an electro-magnetic switch I which comprises a base plate 2 on which is mounted an actuating unit 3 and a stationary contact unit d. Forming the body of the actuating unit 3 is a field support member 5 composed of a right hand half shell S and a left hand half shell l. The shells S and 'i each have a back wall 8 that abuts the base plate 2 and a front wall 9. Bottom walls I integrally join the walls, B, 9 at the respective base portions of each and middle wall portions Il bridge the respective walls 8, il at a point below the tops thereof. With the shells 5 and 'I against one another, as is more clearly shown in Fig. 6, a window opening I2 and an upper trough like portion I3 are formed that extend through and across the width of the eld support member 5.

The facing surfaces of the shells G and 'i are recessed 'to provide an enclosed cavity I4 that extends about the window I2 and which is shaped to closely receive an actuating coil I5. The coil I5 is of tubular configuration and is comprised or roughly concentric turns wound to conform to the shape of the cavity I4. Terminals It and H' are attached to the coil l5 and extend from within the cavity I/-l through appropriate slots in the front walls 9 of the eld support member 5 to the exterior, thus providing convenient means for the attachment of energizing leads which are not shown. The coil may be iixed within the cavity of the leld support member 5 by forming it oi such size as to fit snugly within the cavity so as to require no iurther support, as shown, or the coil may be ceu mented or potted in the member 5 to give greater support and to improve heat dissipation.

The right hand and left hand shells 6 and l are secured to one another so as to form a unitary member 5 by bolts I8 or other suitable fastening means passed therethrough. The member 5 is oriented with respect to the base plate 2 by tongues i9 which project rearwardly from each back wall to be received snugly within a rectangular opening 22 near the bottom oi' the plate 2.

Disposed within the trough like portion I3 of the member 5 is a stationary inverted U-shaped magnetic yoke 22 having downwardly extending legs overhanging `beyond the sides of the half shells 5 and l. The yoke 2I is comprised of a plurality of magnetic laminations 22 stacked in two groups that are separated by an air gap 23 extending for the full width of the magnetic portion of the yoke 2l so as to interrupt the flux path. Disposed at either side of the stacked laminations 22 is one of a pair of side plates 24 bound in place by rivets 25 which extend through the laminations 22 and the side plates 24 to clamp the yoke elements tightly to one another. The plates Ztl are formed thick enough to have adequate strength to maintain the tightly compressed relation of the laminations 22 and preferably are formed of a material that will not :provide a flux path shunting the air gap 23. High reluctance stainless steel has been found to be a material adequate for this purpose.

The two downwardly facing end surfaces 26 at the lower ends of the legs of the U-shaped yoke 2E are disposed slightly beneath the middle wail portions il that form the upper limit of the window opening I2. Each of the surfaces 2G is slotted to receive a shading coil 2l and the surfaces 25 are ground flat and coplanar to provide a pair of sealing surfaces against which the armature of the electro-magnetic actuator may rest or seal upon attraction of the armature toward the yoke 2|.

A mounting bolt 28 provided with a lock washer is passed through the 'front walls 9 of the member and thence through the yoke 2i and the rear walls of the member 5 from which the threaded end emerges to be received in a tapped hole 2S in the base plate 2, The bolt 28 may be of magnetic material in which case its diameter should be small enough to leave a suitable air gap between it and the two lamination stacks 22 that will maintain the eiectiveness of the air gap 23. Drawn up tightly, bolt 25 acts as a single fastening which secures 'the entire assembled ield structure comprising the support member 5, the coil I5 and the magnetic yoke 2I in place. As shown in Figs. 2 and 3 the bolt 28 sup-ports the yoke 2l in a position such that there is a perceptible clearance between it and the half shells 6, I to permit the yoke 2| when acted upon by a suicient force to overcome the clamping friction applied by bolt to pivot slightly. The plane of the seal surfaces 26 is thus capable of limited accommodating movement about the axis of the bolt 22 when sumcient force is applied for purposes to be hereinafter described.

Carried by and in siidable engagement with the field support member is a stirrup shaped armature carrier 32 that extends around the outside of the coil il and straddles the yoke 2I. The configuration of the carrier 3S is shown more clearly in 8. The carrier 3S is a unitary integral insulating element comprising primarily, a Contact carrying horizontal cross bar portion 3i, and two downwardly extending legs 32. A pair of notches 23 let into the cross bar 3l slidingly nt closely about tongues 34 that project ring l2tof the member "5.

the middlewall portions i i. wardextentoiy seal surfaces 26 must be greater 'than'thefover-lap of ther guiding surfaces so thatr iuponlfremovalloif'the'bolt v28 the armature 31 and managers '"5 fromrthe: front walls 119 and 'back walls 8 cof'f the -nel'df support member r`5, las is f shown-in `Eig. 16.

.',Thernotches 33 and tongues 341 slidably., engage ione -another L. to provide 1 upper alignment :guides :for :theicarrier 3l] that restrict movement to a 'verticalstraight lineaction The lower .ends of :the legs :sof e'the'armature carrier. 3@ are turned inwardly toterrninate in spaced pads .35 which bear -with'a'freely sliding t against the sidesvof the-.bottom `walls Iii lof the iield -support Imemf .ber-5. :Thefpads iixare retained against sidewise movement by projections-33 -formedaas .an integral part of the memberlil. A set of lower alignmentyguides is thus provided, whichin confiunctionswith the `upper'alignment guides mounts the carrieres!) `for non-binding vertical'mcvement.

fFitted between the lower portions of the legs :-32fof-the armature carrier' Sil yis a magnetic armaturef3' that extends through the window kopening tenons'cformed'as a part of the armature ,l 351 below the slots 3Q, form a dovetail connection between theypads '35 and ribs il@ to provide a vloose but permanent connection between the carrier 3!! .and the armature-3?. The metallic'parts making' up the magnetic circuitof .the actuating kunite are called upon to perform no part in the ,guiding of' thearmaturecarrier and contact assembly. The armature 3l is located longitudinally `by the armature carrier E13-and is approximately centered -in it 'laterally bythe back wall .S-andafront wall 9 of field support member 5 -.which -form twosides of window i2. Walls 8 and -.-9.areso spaced as to permit free-motion of armature-3l 4toward and away from yoke 2 l. By forming. thecarrierxiand eld support'member 5 of `a material such as phenol-aldehyde resin or the likes-.dry bearing surfaces can be provided that twill. vgive long .life .with only `small amounts .of

wear.

YTheaarmaturev'l is thus mounted tomove .transversely with respect to the axis of the coil [5.

=The `carrier 30 and armature 3l forman assembly which moves as a unit Vwhenever'the armature 3l is moved upward in response to mag-` netic attraction between the armature 31 and the yokeA 2l. Likewise, a release of the armature. 3'! Vfrm..closed.orsealed position with respect to ythe yoke 2 iacauses downward movement in unison of .both the armature 3'! and carrier ,3o. The

.downward travel is varrested when the bottom .surface of the armaturek 3l contactsl the upper surface ofthe bottomwall H3. The molded armature carrier fit-is thus relieved of the direct impact stresses arising out of ythe arresting of downward travel yof the armature upon deenergization, .'Such stresses are instead absorbed bythe iieldA support member and the armature 3i. The amount of vertical travel of the armature 3l andcarrier 3d is dependent upon the vertical v60 distance between the faces 26 of the yoke 2i and the upper surface of the bottom wall H3 and the armature thickness between these two surfaces. The mating guide surfaces for the armature carrier'iw, which are part of the notches 33 and "tongues'Sli and of the pads 35 and projections "it, ."*overlapA one anotherby an extent greater than the amount of armature travel-to ensure "that themcarrier4 3d is-oaptively retained in all operatiligpositions. The extent of overlap of the guide 4surfaces is related to the downward extent ofthe seal surfaces 2t of the yoke 2| below The mount of down- Downwardly projectl four openings?Y fil. 45 f.

`carrier-:3D and wyokezd I"mayiiberfmevedupwardly .to disengagesthefguiding surfaces vtc-permit asasembly and disassembly.

The armaturerl"is;,composed of a stack of :laminations :dl ofA ferro-magnetic material -prolviclinga :low reluctance flux path. A-paircf side .platesllareplacedfat the sides of the lamina- :tions and rivetsf'dexdisposed yas kshown hold the laminations ,fil `and :the side plates 42 in place. The upper surface .Q4 of fthe `:armature '3l is ground flat and isslottedfatr voverthe .areas facingand iny alignment with the shading coil slots. *.-Similar slots-Stein ,alignment with the innerfedges-foiwthe yoke-sealing faces2 `set oilE and deiine a pairfofgarmature sealing faces 45 that seal against thesurfaces 2E of the yoke 2| when/the: armature Vassembly is raised to closed position. The-working iiux circuit comprises a .singlev loop or lpath thatintersects each of the sealing surfacesso thatfseparation of either pair of surfaces .interrupts thefentire working fiux.

As has ybeen noted, the yoke 2| is permitted a limited accommodating vmovement about the l mounting bolt 28 when suincient force is applied. This force-is lordinarilyprovided by impact of the armature vupon sealing.

Lateral alignment of the'seal surfaces 2t with the seal'faces t5 is thus brought-about-as a normal function o the ofmagnet. 'To provide for transverse alignment,

lhorizontal line perpendicular to 'the bolt 2t, the

that is to permit the armature to rotate about a armatureftl is mounted'loosely in the carrier Si) with suincientclearance topermit it to rotate slightlyfto seal against' yoke 2i without com municating av corresponding binding `motion to lthefcarrier 35. YBecause yof this yfreedom of accommodation andbecauseof the near absence vofv any magnetic side pull which can be com- -municatedto thecarrier, the carriere@ moves with a minimum of friction and wear.

v Comprising an integral'part of the cross bar portion 3| vof" the armature'carrier-Sil is an upwardlyextending rib Mi through which extend A movable bridging contact :i8 iSv-extended through each opening il and a contactspring 4S compressed between. each contact '18 and thecross 'bar -3l retains -thecontacts $8 in an upper position. vMovement of the armature from open to closed position causes a like 4movement of the bridging contacts is which are'zbrought into engagement vwith stationary `contacts to befdescribed.

` Extending outward from the base plate 2 and over the actuating unit 3 is anarc hood di) tight- .ly secured by a pair ofgmounting boltsv iii. vThe hood titl is formed with a rear wall 52 fromwhich extend inv a` forward directionY side walls i at v either end or" the wall 52 and three partition walls 5i spaced evenly between the end walls 53. A iront wall t5 extends across the forward ends of the walls 53, 5i. to provide four open bottomed arc restricting chambers, each chamber being adapted yto vreceive one of 'the movable bridging 'into nan. engaging nutv 'Si maintain the terminal 4 Vboards"E 55 irr place. "-lhus,-A there is l'provided v a unitary sub-assembly for each set of stationary contacts that may be easily removed from and inserted in the arc hood 50 for such purposes as inspection or replacement of contacts.

In Fig. 4 there is shown a modification of the switch of Figs. l, 2 and 3 that has a supplementary magnetic yoke extending beneath the coil. Like parts of the modiiied switch of Fig. 4 and the switch of Figs. 1, 2 and 3 are designated by like reference numerals. The modication has a field support member 6I composed of left and right hand half shells 62 and 53 that are notched to receive a supplementary magnetic yoke Se that is snugly tted along the sides and bottom of the member 6i. The yoke 64 is disposed directly beneath the armature 31 with a small gapbetween each vertical leg of the yoke 64 and the armature 37 when in lower position. Yoke 54 is formed of magnetic sheet material to form a relatively low reluctance leakage ux path and its spaced relation with the other magnetic and electrical components of the electro-magnetic are shown in perspective in Fig. l0.

With the electro-magnetic switch of Figs. l, 2 and 3 in open position the armature 31 rests upon the bottom walls IB and excitation of the coil i5 produces leakage iiux that extends through the armature 3l and thence downward and about the underside of the coil I5. An appreciable downward pull is exerted upon the armature 3i by this leakage ux the attractive force of which is in opposition to the attractive force between the armature 31 and the yoke 2l. The net eiiect is to increase the pick-up voltage over that which would exist in the absence of such a downward pull. The relation of the coil i5 and the magnetic components comprising the yoke 2| and the armature 31 is shown in Fig. 9 to aid in a visualization of the spacing of the parts.

While the magnet of this invention ordinarily can be proportioned to provide the desired characteristics for actuating a switch without the use of supplemental yoke (ill, the ease and economy with which these characteristics may be changed to meet unusual requirements by the addition or modification of supplemental yoke Gli is a further feature of value.

For example, if a. given magnet constructed in accordance with this invention is arranged to actuate a switch imposing an opening bias such that applied voltage of sixty percent of normal operating voltage will cause pick-up but eighty percent voltage is require to compress the contact springs and it is desired to raise the pick-up voltage to eighty percent of normal voltage, a supplemental yoke B4 having a comparatively small cross-sectional area may be inserted. rIhe increased counteracting attractive force produced by this yoke is effective to a perceptible degree only when the magnet is in near open position. Once the magnet starts to move, this counteracting attractive force diminishes very rapidly, becoming substantially zero when the armature has moved to a point well in advance of sealed position. By varying the cross-sectional area of the supplementary yoke 6d or its location or both, the counteracting attractive force characteristic may be varied and the pickup voltage altered as desired. In this way it is possible to modify the magnet characteristics to meet special requirements in a very simple and economical manner.

To sufhciently demagnetize an electro-magnetic actuator so that the armature will return to open position upon deenergization of the operating coil an air gap is customarily incorporated in the magnetic circuit. Since reduction of the length of the air gap may cause sticking due to residual flux, it is desirable to have the air gap unaiected by wear of the sealing surfaces. In the magnet oi' this invention the air gap is located wholly within the yoke 2| and is not subjected to change due to wear of the sealing surfaces and its length may be accurately set at the minimum length necessary to prevent sticking. Placing the air gap in the yoke outside of the coil is an added advantage in that less magnetizing current is required than would be required for the same gap disposed in that portion of the magnetic circuit within the coil.

To obtain satisfactory operation of a transversely movable armature of the type employed in this invention its movement must be guided against side play, oblique movements or tilt. To this end the external carrier 3Q, engaging the ends of the armature 3l, slides in contact with mating surfaces on the eld support member 5 disposed to compel straight line motion of the carrier 3i! in which each position assumed by the armature is parallel to every other position. The wide spacing of the guide surfaces in the direction of motion aids movement of the armature assembly without binding and without concentrated stresses which could give rise to wear.

The housing 5 is advantageously made of electrical insulating material since such simplifies the mounting of coil l5. Where the magnet is employed for the actuation of switch contacts it is also of advantage to construct the carrier 3d ci electrical insulating material. Since these parts are also the main parts in sliding engagement, the organic electrical insulating materials such as the various condensed or vulcanized polymers, resins and plastics are preferred, because substances or" this class have excellent long wearing dry bearing properties under the type of loading imposed thereon in the apparatus of this invention.

I claim:

l. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic eld yoke providing a flux path between the ends of said coil outside of said coil, a magnetic armature within the opening of said coil attractably movable with substantially translational motion transversely with respect to said opening toward a closed position with said iield yoke upon energization of said coil and biased to move away from said closed position, a carrier joined to said armature for movement therewith, and stationary guides having guide surfaces slidably engaging said carrier adapted to guide said armature and said carrier in their translational movement toward and away from closed position.

2. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic iield yoke providing a flux path between the ends of said coil outside of said coil, a magnetic armature within the opening ci said coil attractably movable with substantially translational motion transversely with respect to said opening toward a closed position with said iield yoke upon energization of said coil and biased to move away from said closed position, a carrier joined to each of the ends of said armature and extending about the exterior of said coil, said armature and said carrier forming an armature assembly movable as azunitand linked with said coil, and stationary guides having guide surfaces slidably engaging said carrier adapted to guide said armature assembly upon movement of said armature in translational motion toward and away from said closed position.

3. In an electro-magnetic actuator the coinbination comprising a coil having an opening cxtending longitudinally therethrough, a magnetic field yoke extending the length of said coil along a portion of the outer surface thereof turning over and about the end faces of said' coil and terminating in a pair of sealing surfaces disposed respectively at the opposite ends of said coil, a magnetic armature extending through 'the opening of said coilmovable transversely with respect to said opening toward and away from closed position with respect to said field yoke, said armature having sealing face areas adapted to closeagainst the sealing ysurfaces of said yoke, azcarrier joined to the ends of said armature and extending about the outer surface of said coil toform an armature assembly with said armature, .and stationary guides having guide surfaces slidably engaging said carrier :adapted to guide said armature assembly upon movement of said armature toward and away from said closed position.

4. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic field yoke disposed in flux conducting relation with respect to said coil, a magnetic armature disposed in flux conducting relation with respect to said coil vattractaloly movable transversely with substantially translational motion with respect to the opening in said ycoil toward la closed position with said eld yoke upon energization of said coil and biased to move away from said closed position, a carrier extending around the outside of said coil connected to the ends of said armature, and stationary guides having guide surfaces slidably engaging said carrier for `guided translational movement of said carrier and said armature.

5. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic eld yoke extending lengthwise of vand outside of said coil overhanging the ends of said coil, an armature extending through the opening in said coil attractably movable transversely with substantially translational motion with respect to said opening toward a `closed position with said neld yoke upon energization of Asaid 4coil and biased to move away from said c-'losed position, a carrier movable with said armature extending the length of said coil across the outer surface thereof and turning about and extending along each end of said coil to connections with armature, and stationary guides having guide surfaces slidably engaging said 'carrier for guided translational movement of said armature and carrier.

6. In an electro-magnetic actuator the combination comprising la coil having an opening extending longitudinally therethrough, magnetic eld yoke extending the length of said coil along one side of the outer surface thereof and overhanging beyond the ends of said coil, a inagnetic armature extending through the opening of said coil attractably movable transversely with respect to the opening in said coil toward closedposition with said field vyoke upon energ-ization of said `coil and biased to move vaway from said 'closed position, a vcarrier movable'with said armature having a cross member extending the length of said coil across the outer surface thereof and legs integrally joined with said cross member each extending respectively along an end of said'coil and connected with armature, and stationary guides having a iirst set of vguide surfaces slidably engaging said cross member and a second set of guide surfaces spaced from said first set `slidablyengaging said legs.

7. In an electro-magnetic actuator the combination comprising ra coil having an opening extending longitudinally therethrough, 'a magnetic eld yoke extendingr the length of said coil across the top thereof and overhanging the ends of said coil, a magnetic armature 'within the opening in said coil movable transversely with substantially translational motion with respect to said opening'to .and from closed' position with respect tosaid neld yoke, a carrier straddling said eld Ayoke having a cross lmen1- ber extending across 'the top Aof saidneld 4yoke and legs joined to said cross .member extending downwardly beyondthe ends fof' said coil and foonnected with said armaturepand stationary guides having guide surfaces slidably engaging said cross member above said yoke and said vlegs :beneath said yoke to guide said yoke and farmature with substantially translational motion.

'8. In an electro-magnetic actuator the com bination comprising a `coil having a horizontal opening extending longitudinally therethrough, a tubular non-magnetic lining extending through the opening of said coil, a magnetic .field yoke disposed l.above .said coil with end portions extending downwardly along the ends ici said coil terminating in a pair of armature engaging surfaces rdisposed Yrespectively vat the opposite fends of said coil opening, a magnetic armature extending through said Atubular lining normally resting thereon, 'said armature being movable transversely -withvirespect ato the opening ins'aid coil vbetween l'said yposition of 'rest and a position of engagement with said armature engaging surfaces of said kyokeupon alternative deenergization and energization of lsaid coil, -a carrier movable wlith said armature 4extending the length of said coil across vthe outer surface thereof and the ends of said coil to connections `with said armature, and stationary .guides having guide surfaces slidably. engaging said carrier for guided .movement/'of said ycarrier and said armature.

9. In an electro-magnetic actuator the 'come bination comprising a coil 'having an 'opening extending .longitudinally therethrough, 'a magnetic field yyoke extending lthe length of said coil .along a .pcrtionpof the outer surface th. 'eof and overhanging the Aends of said fcoil, said -e'ld yoke comprising 'a rpair 'of closely adjacent lainination stacks spaced from yo-ne another by a small air gap transverse to field flux inducedoy said ycoi-l, `a inagii'etic:aiimature extending through the openinguof said coil movable transversely with .respect` thereto! toward andv lawayfrom said eld yoke member upon respective alternate energization and deenergization of said `ooi-l, a carrier joined to and-movable with said 'armature extending the length of lsaid coil -across the outer surface thereof and about the Iends of said Icoil to connections W-i-thsaid armature, and stationary guides for said carrier and said armature 1-0. 'In an-electro-magnetic actuator the combination Vcomprising fa 'fcoil having an opening extending longitudinally therethrough, a main magnetic eld yoke disposed adjacent one side of said coil, a supplementary yoke disposed adjacent the opposite side of said coil, a magnetic armature within the opening of said coil attractably movable transversely with respect to said opening upon excitation of said coil toward a closed position with said main field yoke in opposition to attractive force initially prevailing between said supplementary yoke and said armature and biased to move away from closed position toward said supplementary yoke, and a guided carrier joined to said armature for movement therewith.

11. In an electro-magnetic actuator the cornbination comprising a coil having an opening extending longitudinally therethrough, a magnetic main field yoke extending the length of said coil along a portion of the outer surface thereof and over-hanging the ends of said coil, a magnetic armature extending through the opening of said coil movable transversely with respect thereto, said armature being adapted to move to closed position with said main yoke upon excitation of said coil and being biased to a normally open position at the side of the opening of said coil opposite said main yoke, a supplementary yoke of magnetic material disposed outside said coil adjacent the open position of said armature to provide a flux path by-passing said eld yoke member, and a guided carrier movable with said armature extending the length of said coil across the outer surface thereof and along the ends of said coil to connections with said armature.

12. In an electro-magnetic switch the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic eld yoke providing a flux path between the ends of said coil outside of said coil, an armature of magnetic material extending through the opening of said coil movable transversely with respect to said opening toward and away from said field yoke, a carrier joined with the ends of said armature extending about the exterior of said coil, a movable contact cross bar secured to said carrier, stationary guides having guide surfaces slidably engaging said carrier and adapted to guide said armature assembly toward and away from said yoke, a plurality of movable bridging contacts mounted upon said contact cross bar, a stationary Contact arc hood comprising front, back and side walls and a top wall panel, a plurality of openings in said top wall panel one of each disposed above one of said movable bridging contacts, a plurality of removable stationary contact mounting strips each detachably mounted upon said arc hood to cover one of said plurality of openings, and a pair of stationary contacts mounted on each of said mounting strips in alignment with said bridging contacts for engagement and disengagement therewith.

13. In an electro-magnetic switch the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic field yoke extending the length of said coil along a portion of the outer surface thereof and overhanging beyond each end of said coil, a magnetic armature extending through and movable transversely with respect to the opening in said coil to and from closed position with respect to said yoke, a movable contact cross bar mounted on said armature for movement therewith, a plurality of movable bridging contacts resiliently mounted on said cross bar, an open bottomed arc hood comprising front, back and side walls and top wall ribs extending between said front and back wall panels spaced from one another and said side wall panels to form a plurality of openings each disposed in line with one of said movable bridging contacts, a plurality of removable stationary contact strips each detachably mounted upon said arc hood to cover one of said plurality of openings, and a pair of stationary contacts mounted on each of said mounting strips in alignment with said bridging contacts extending from within said arc hood to the exterior to form terminals.

14. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic field yoke providing a flux path between the ends of said coil disposed outside of said coil and having armature abutting sealing surfaces adjacent the ends of said coil opening, pivotal mounting means engaging said yoke to mount the same for limited accommodating tilting movement of said sealing surfaces about an axis transverse to said coil opening, and an armature extending through said coil opening reciprocatably movable transversely with respect to the opening in said coil having seal faces engageable with said yoke sealing surfaces upon movement of said armature toward said yoke, said armature being mounted for limited accommodating tilting movement about an axis extending lengthwise thereof and perpendicular to the axis of pivot of said yoke.

15. In an electro-magnetic actuator the combination comprising a field support member, a coil having a central opening extending lengthwise thereof carried by said eld support member, a magnetic field yoke providing a ux path between the ends of said coil about the outside of said coil having sealing surfaces adapted to abut an armature, a pivot mounting engaging said eld yoke and said eld support member supporting said yoke for limited accommodating pivotal movement, a magnetic armature within the opening of said coil having seal faces adapted to abut said sealing surfaces of said yoke and being biased to an open position with said seal faces spaced from said sealing surfaces of said yoke, said armature being attractably movable transversely with respect to the opening in said coil toward said field yoke upon energization of said coil and adapted to strike said yoke an impact blow to cause limited accommodating movement of said yoke to align said sealing surfaces with said seal faces.

16. In an electro-magnetic actuator the combination comprising a field mounting member, a coil having a central opening extending longitudinally therethrough supported by said mounting member, a magnetic field yoke extending the length of said coil along one side of the outer surface thereof and about the ends of said coil terminating in a pair of armature engaging sealing surfaces, a pivot mounting attaching said yoke to said mounting member for limited accommodating pivotal movement about an axis transverse to the coil opening, a magnetic armature extending through the opening of said coil and movable transversely thereof to and from a closed position with respect to said yoke, said armature having seal faces disposed in facing relation to the sealing surfaces of said yoke and adapted for engagement therewith upon movement of said armature to said closed position, an armature carrier connected to and movable with said armature having a central portion extending the length of said coil along a portion of the outer surface thereof and a pair of leg portions each joined to said central portion and extending along the opposite endsv of said coil, said leg portions loosely engaging and supporting lsaid armature for limited accommodating movement permitting tilt of said armature seal faces about a longitudinal axis perpendicular to the axis of pivot of said yoke, and stationary guides slidably engaging said armature carrier guiding movement of the same transversely with respect to the opening in said coil.

17. In an electro-magnetic actuator the combination comprising a iield support member having spaced rear and front walls, a bottom wall spanning the space between said rear and front walls at the lower extremities thereof, a medially disposed bridging wall spaced above said bottom wall and spanning the space between said rear and front walls to form therewith a window opening extending through said support member, said support member having a cavity extending about said window opening; a coil fitted within the cavity of said support member; a magnetic field yoke disposed adjacent said bridging wall providing a flux path between the ends of said coil about the outside of said coil; a pivotal mounting member extending through said rear and front walls and said yoke supporting said yoke; a magnetic armature extending through said window opening movable transversely with respect to said window opening toward and away from closed position with respect to said neld yoke, said armature being biased to move away from said closed position and being movable upon excitation of said coil to said closed position; an armature carrier straddling said field support member and joined to the ends of said armature for movement therewith; and guides mounted on said eld support member slidably engaging said armature carrier adapted to restrain said armature carrier to transverse movement with respect to said window opening.

18. In an electro-magnetic actuator the combination comprising a coil having an opening extending longitudinally therethrough, a magnetic yoke extending about the outside of said coil terminating in armature engaging sealing surfaces at the ends of said coil, a magnetic armature extending through the opening of said coil with seal faces disposed in facing relation to the sealing surfaces of said yoke forming with said yoke a working flux path, said armature being biased to an open position within the opening of said coil .remote from said yoke providing when in said open position a leakage ux path linked with said coil about a segment thereof remote from said yoke establishing an attractive force upon said armature when in said open position upon excitation of said coil which is in opposition to the attractive force of ux prevailing in said yoke, said armature being movable transversely of said coil opening to a closed position with said yoke against the opposing attractive force of said leakage flux path upon excitation of said coil.

19. An electro-magnetic actuator comprising a coil having an opening, a magnetic yoke, a non-magnetic elcl support member supporting said coil and yoke in such position that said yoke partially surrounds said coil, a magnetic armature extending through the opening in said coil, and a slide member engaging said armature slidably related to said frame to allow movement -14 of .said larmature v with substantially .translational motion transversely to the opening in said coil tocomplete the magnetic circuit of said yoke.

20. An electro-magnetic actuator comprising a non-magnetic field support member, a coil having an opening mounted upon and surrounded by .said field support member, a slide member slidably related to said eld `support member to allow movement `of said ymember transversely to the opening in said coil, a magnetic yoke mounted on said field support member in such position that said yoke partially surrounds said coil, and a magnetic armature extending through the opening in said coil mounted on said slide member to allow movement of said armature transversely to the opening in said coil to complete the magnetic circuit of said yoke.

2l. An electro-magnetic actuator comprising a field support member of insulation material enclosing a coil having an opening therein, said field support member having an opening concentric with the opening of said coil, a carrier supported and guided by said field support member, a field piece providing a iiux path exterior to said coil between the ends of said opening, and an armature extending through said opening in the field support member and connected to said carrier whereby on current flow through said coil said armature will be attracted toward said field piece to actuate said carrier.

22, In an electro-magnetic actuator a coil having an opening therethrough; a non-metallic housing for said coil having an opening aligned with the opening in said coil, stationary armature guiding surfaces, and a mounting shoulder; a field member extending lengthwise of the exterior of said coil and housing overhanging the ends thereof and abutting the mounting shoulder of said housing; a transversely movable armature including movable guiding means slidably engageable with said stationary guide surfaces, extending through the opening in said coil, and adapted to abut the overhanging ends of said field member when the latter is in mounted position, said armature being insertable within the opening in said coil and housing prior to the mounting of said field member; and fastening means engaging said field member and said housing mounting shoulder to secure said field member in mounted position in relation to said housing and to limit the excursion of said armature to a path precluding disengagement of said movable guiding means from said stationary guiding surfaces.

23. An electro-magnetic actuator comprising a eld support member of insulating material having an opening, a coil mounted in said field support member and surrounding said opening, a carrier member of insulating material slidably related to said field support member to allow said carrier member to move transversely to said opening, a magnetic yoke mounted on said field support member in such position that said yoke partially surrounds said coil, a magnetic armature mounted in said carrier member and extending through said opening to allow movement of said armature transversely to said opening to complete the magnetic circuit of said yoke.

24. An electro-magnetic actuator comprising a field support member of insulating material having an opening, a coil mounted in said field support member and surrounding said opening, a carrier member of insulating material slidably related to said field support member to allow said carrier member to move transversely to said 15 16 opening, a magnetic yoke mounted on said eld References Cited in the file of this patent support member in such position that said yoke UNITED STATES PATENTS partially surrounds said C011, said magnetic yoke having an interruption providing a high reluc- Number Name Date tance gap exterior to said coil, a magnetic arma 5 212931823 Hlckmfan et al Aug' 25 1942 ture mounted in said carrier member and eX- 212971423 Matthlas Sept" 29 1942 tending through said opening to allow move- 213781022 Logap June 12 1945 ment of said armature transversely to said open- 4311377 Durbm et aL No 25 1947 ing to complete the magnetic circuit of said yoke. 

